DEVELOPMENT OF HIGH TEMPERATURE OXIDES WITH SUPPRESSES OXYGEN DIFFUSIVITY

THE SUCCESSFUL DEVELOPMENT OF HIGH-TEMPERATURE CERAMICS OR CERAMIC COMPOSITES FOR USE IN COMBUSTION ENGINE ENVIRONMENTSWILL REQUIRE DEVELOPMENT OF THERMODYNAMICALLY STABLE OXIDES FOR PROTECTIVE COATINGS OR AS THE MATRIX MATERIAL IN WHISKER- OR FIBER-TOUGHENED COMPOSITES. THIS PROGRAM WILL DEVELOP CUBIC FLUORITE RELATED OXIDES (BASED ON Y2O3) WITH STRUCTURES MODIFIED BY SELECTED DOPING. THE MODIFICATIONS SHOULD REDUCE OXYGEN DIFFUSIVITY BY TWO TO FOUR ORDERS OF MAGNITUDE. IF THIS CAN BE ACHIEVED, THIS OXIDE MAY PROVIDE OXIDATION PROTECTION TO MUCH HIGHER TEMPERATURES THAN CURRENTLY POSSIBLE, WHILE RETAINING A HIGH THERMODYNAMIC STABILITY. THE MATERIALS DEVELOPED WILL EXTEND THE USE OF SIC, SI3N4 OR CARBON FIBER BASED CERAMICS TO THE HIGHEST POSSIBLE TEMPERATURES, IN COMBUSTION ZONE ENVIRONMENTS.